Cam for composite camshaft

ABSTRACT

A cam with a bore that has a funnel-shaped core-insertion section. To ensure that the cam will rest more securely against the core and remain more precisely centered, the section ( 5 ) comprises at least two mutually aligned conical extents ( 6  &amp;  7 ), each expanding outward at a different apical angle.

[0001] The present invention concerns the design of a cam for acomposite camshaft for controlling the valves in internal-combustionengine and featuring the characteristics recited in the preamble toclaim 1.

[0002] Cams and camshaft of this genus are described in German 4 121 951C2. The core of the shaft differs in thickness along its length, and, tofacilitate sliding the cam over it, the cam is provided with a cavitythat tapers out like a funnel at least part-way along at least one side.The outside diameter of the opening into the cavity is at least as longas the ridges or webs that constitute the thicker sections of the core.The conical expansion extends at least ⅕ of the thickness of the cam andhas an apical angle of approximately 20 •.

[0003] This design has drawbacks. First, in spite of the funnel-shapedexpansion, considerable force is required to mount the cams.Furthermore, it is difficult to keep the cams precisely centered on thecore.

[0004] The object of the present invention is a cam with a bore that hasa funnel-shaped core-insertion section ensuring that the cam will restmore securely against the core and remain more precisely centered.

[0005] This object is attained in accordance with the present inventionby the characteristics recited in the body of claim 1.

[0006] Advantageous further and more advance embodiments are addressedin the subsidiary claims, 2 through 8.

[0007] One embodiment of the present invention will now be specified byway of example with reference to the accompanying drawing, wherein

[0008]FIG. 1 is a perspective view of q composite camshaft,

[0009]FIG. 2 a view of a single cam,

[0010]FIG. 3 illustrates a cam and a core before the core has beenforced onto it,

[0011]FIG. 4 illustrates the cam forced onto the core,

[0012]FIG. 5 is a section through the cam, and

[0013]FIG. 6 is a larger-scale depiction of the detail VI in FIG. 5.

[0014] The composite camshaft illustrated in FIGS. 1 through 4 comprisesa core 1 that cams 2 can be forced onto. The shape of each cam 2 and itsorientation in relation to core 1 will be dictated by the specificationsof the particular internal-combustion engine. The core 1 of theillustrated embodiment is a hollow cylinder with corrugations 3 thatconstitute seats for cams 2. Each cam 2 is provided with a bore 4 thatis essentially narrower than corrugations 3. The cam's core-insertionsection 5 is funnel-shaped and at least as wide as corrugations 3.Corrugations 3 are compressed when cams 2 are forced over them,resulting in a plastic but resilient deformation that ensures a tightfit between the cams and the core. Cams 2 are, at least in the vicinityof bore 4, usually harder than core 1.

[0015]FIGS. 5 and 6 illustrate the core-insertion section 5 of a cam 2in detail. Section 5 comprises two conical extents 6 and 7 of differentlength and apical angle. Apical semi-angle 8 is 2 •. The apical angle ofouter conical extent 7 is 20 •, its semi-angle 9 accordingly equaling 10•.

[0016] The length 10 of outer conical extent 7 is 0.09 the thickness 11of a cam 2.

[0017] Depending on the specifications, core-insertion section 5 maycomprise more than two mutually aligned conical extents. This featurecan be particularly practical when cams 2 have a very considerablethickness 11.

1. Core-insertion section in the shape of a funnel in the bore (4) of acam (2) that can be forced over the core (1) of a composite camshaft,characterized in that the section (5) comprises at least two mutuallyaligned conical extents (6 & 7), each expanding outward at a differentapical angle.
 2. Core-insertion section as in claim 1, characterized inthat the mutually aligned conical extents (6 & 7) expand by s factor ofthree to five.
 3. Core-insertion section as in claim 1, characterized inthat the mutually aligned conical extents (6 & 7) expand by a factor offive.
 4. Core-insertion section as in claim 1, characterized in that,when there are two mutually aligned conical extents (6 & 7), the apicalangle of the inner conical extent (6) is 3 to 5 • and that of the outerconical extent (7) is 15 to 25 •.
 5. Core-insertion section as in claim1, characterized in that, when there are two mutually aligned conicalextents (6 & 7), the apical angle of the inner conical extent (6) is 4 •and that of the outer conical extent (7) is 20 •.
 6. Core-insertionsection as in claims 1 to 4, characterized in that the mutually alignedconical extents are reduced from inside to outside.
 7. Core-insertionsection as in claim 6, characterized in that, when there are twomutually aligned conical extents (6 & 7), the length (12) of the innerconical extent (6) is 0.30 to 0.40 and the length (10) of the outerconical extent (7) is 0.08 to 0.12 times the thickness (11) of the cam(2).
 8. Core-insertion section as in claim 6, characterized in that,when there are two mutually aligned conical extents (6 & 7), the length(12) of the inner conical extent (6) is 1 to 3 mm and the length (10) ofthe outer conical extent (7) 3 to 6 mm.